A mechanism providing an essential enhancement of the conversion efficiency of a single high harmonic in gaseous media is first proposed using an appropriate change in the phase mismatch and group-velocity mismatch in the vicinity of resonance.

A group-velocity mismatch compensation technique has been applied to cw Nd:YAG and Nd:YLF lasers mode locked by use of the nonlinear reflectivity or the nonlinear phase shift that arises from the intracavity parametric interaction of a pulse with its second harmonic. An intracavity birefringent plate, which delays the fundamental wavelength pulse with respect to the second-harmonic pulse, compensates for the opposite effect that arises in the second-harmonic crystal. Compensation reduces the pulse duration by a factor of 2 and allows pulses of 5.1 and 5.9 ps to be obtained from Nd:YLF and Nd:YAG lasers, respectively. {copyright} 1995 Optical Society ofmore » America« less

Group-velocity mismatch between the pump and Stokes pulses and the inertia of optical nonlinearity are shown to modify scenarios of slow-light evolution of laser pulses accompanying stimulated Raman and Brillouin scattering (SRS and SBS) of light. In the transient regime of SRS and SBS, the inertia of nonlinear polarization of a medium shifts the peak of an amplified Stokes field envelope relative to the input Stokes pulse. This shift is sensitive to the shape of input laser pulses and is controlled by the SRS and/or SBS gain, the damping time of the optical phonon wave, and the delay time betweenmore » the input pump and Stokes pulses. In the regime where both the inertia of nonlinear polarization of an SRS medium and group-delay effects are significant, stationary modes of the Stokes field may exist in the frame of reference propagating with the group velocity of the pump field. The maximum group delay attainable for such modes of the Stokes field is limited, similar to the steady-state regime, by the ratio of the steady-state SRS gain to the Raman gain bandwidth.« less

Equations describing acousto-optic diffraction of ultrashort laser pulses in an anisotropic medium are derived, taking into account the group velocity mismatch of optical eigenmodes. It is shown that the solution of the modified coupled-mode equations taking into account the group delay is characterised by an increase in the pulse duration, a decrease in diffraction efficiency, a change in the shape of the wave packet envelope, as well as by an increase in the width of the transmission function.

The direct scattering problem for an inhomogeneous lossy medium is examined for the one-dimensional case in which the phase velocity profile is discontinuous at the boundaries of the medium. Scattering operators (or impulse responses) and propagation operators are defined and equations that govern their behavior are developed. Knowledge of the scattering kernels for one round trip in the medium implies that the scattering kernels can be determined on any time interval. Numerical examples are presented. It is also shown that this scattering problem is reducible to one in which there are no phase velocity mismatches. This reduction provides considerable numericalmore » advantage in the solution of the direct scattering problem. The inverse problem is examined in a companion paper.« less